This invention relates to a method for the preparation of 2,3-dihydroergolines.
The 2,3-dihydroergolines that can be prepared according to this invention and biologically active compounds, or intermediates useful in the production of biologically efficacious compounds, which exhibit an effect on the central nervous system, see for reference, e.g., U.S. Ser. No. 589,376.
The preparation of 2,3-dihydroergolines per se is conventional and has been described in GB No. 1,596,210. According to this process, the ergoline derivative is reduced with sodium borohydride in trifluoroacetic acid. Although giving good yields for a number of ergoline derivatives, this process disadvantageously leads to dimerization products, e.g. in the cases of lisuride or terguride (cf. N. K. Bach and E. C. Kornfeld, Tetrahedron Letters 3315 (1973). Formation of these dimerization products becomes more pronounced with larger charges of starting material.